Three teenagers were arrested on suspicion of killing a 79-year-old grandmother in her home in Willmar, Minn., authorities said Thursday, easing some residents’ fears but raising new questions about the motive.

Preliminary autopsy results show that Lila Warwick was stabbed multiple times and strangled before she was found late Monday afternoon, said Kandiyohi County Sheriff Daniel Hartog.

The 19- and 16-year-old suspects, both from Willmar, were arrested about 10 p.m. Wednesday. A 17-year-old boy from Willmar was arrested about 1:15 p.m. Thursday.

The case shocked Willmar, a city of 19,500.

Brok Nathaniel Junkermeier, 19, is suspected of second-degree ­murder and first-degree burglary. The 16-year-old is suspected of aiding and abetting second-degree murder and first-degree burglary. A statement from the Sheriff’s Office said only that the 17-year-old was arrested in connection with Warwick’s death.

Lila Warwick

Officials have withheld the names of the 16-year-old and 17-year-old because they are juveniles.

Junkermeier, a 2012 graduate of Willmar High School, has a record of pleading guilty to misdemeanor charges. His Facebook page shows an interest in art, and a SoundCloud page reveals a passion for ­rapping.

He was arrested at the West Central Tribune in Willmar, where he was working in the mailroom Wednesday night, the newspaper said. The 16-year-old was arrested at his home, Hartog said. Both were apprehended without incident, the sheriff added.

Hartog declined to say what led authorities to the teens.

The suspects’ first court appearances are pending. As of Thursday evening, they had not yet been charged.

Warwick’s daughter, Cheri Ekbom, said authorities informed her of the arrests in what “all along has been categorized as a burglary, and I’m quite certain [the suspects] didn’t know my mother. It’s good knowing that [they] are in custody. We’re just trying to move on.”

Hartog declined to address whether Warwick knew the defendants, saying, “I don’t want to get into it right now.” He also would not say what evidence points to suspicions of burglary or whether more arrests are imminent.

Junkermeier is currently on probation. In January, he pleaded guilty in Kandiyohi County to receiving stolen property, a gross misdemeanor. In connection with that case, he had a gross-misdemeanor theft charge dismissed. In February, he pleaded guilty in Stearns County to theft related to a January incident and was put on a year of supervised probation. In June, he was convicted in Meeker County of tampering with a motor vehicle, a misdemeanor.

Warwick

Junkermeier is “a quiet kid” who was picked on in high school, said Ricky Martinez Jr., his former classmate and basketball teammate. Guys would bully him, yelling at him in the halls, he said. “I just think people thought he was an easy target,” said Martinez, who lives in Willmar. “He wouldn’t defend himself.”

But Martinez, 19, took time to get to know Junkermeier, sitting with him in the lunchroom and picking him as a partner during practice. “We would always have nice conversations,” he said by phone Thursday.

So it’s hard for Martinez to imagine the young man killing an elderly woman. “It’s devastating,” he said. “It’s really shocking.”

Deputies were called by someone from Redeemer Lutheran Church in Willmar requesting a check on Warwick, who had eight grandchildren and two great-grandchildren, and helped with office duties and vacation Bible school at the church.

Warwick was supposed to pick up a 14-year-old granddaughter Monday afternoon and take her to the church’s vacation Bible school, but never showed up, said Jennifer Warwick, Lila’s former daughter-in-law.

“We’re all holding up,” said Jennifer Warwick, who is mother to two of Lila Warwick’s grandchildren. “It’s tough.”

Her death has been a big topic of conversation at morning coffee, said Dean Johnson, a longtime Willmar resident, former legislator and member of the University of Minnesota Board of Regents. “When something happens in a town of 19,000, it’s pretty unsettling to folks,” he said.

“We hear about robberies and home entries once in a while, but not to this magnitude,” said Johnson, who didn’t know Warwick. “There’s an undercurrent of, do we need to fear for our safety and our family’s safety?”